The present invention relates to equipment for use with centrifugal, pendulum and other types of broadcast spreaders which distribute dry granular agricultural materials to the soil.
By way of background, a wide variety of equipment is used to apply agricultural materials to the soil surface for use in the cultivation of field crops or for various agricultural purposes. Typically, such applicators are used to spread seeds, pesticides, and/or fertilizers. Applicators have adjustable controls for regulating the rates at which materials are dispensed. Large-scale farming applicators of solid materials or liquid formulations are often pulled by tractors or other power sources over fields. Agricultural spreaders for small-scale applications are usually hand propelled or self-propelled by small engines.
In the case of seed, pesticide or fertilizer applications, optimum or recommended rates of application are generally known. Under-applications of seed result in reduced crops and over-applications are wasteful and expensive or may actually result in reduced yields. In the case of pesticides, proper application amounts are desired for effective control or elimination of weeds, plant diseases, and various insect and plant pathogens. Under-application of pesticides may not provide the proper control and over-application can result in crop damage, unnecessary expense, environmental harm, or injury or risk of injury to application personnel. Similarly, misapplication of fertilizer can have cost implications and result in crop damage or reduced yields as well as potential environmental problems. Agricultural organic chemicals must be handled and applied with great care. Also, the cost of agricultural chemicals has markedly increased in recent years. Avoidance of errors in application is a major economic concern to farmers as well as the agriculture industry.
The literature is replete with various methods and devices related to the delivery and calibration of agricultural spreaders including weighing systems between a tractor and a spreader (U.S. Pat. No. 4,465,211), devices for use with liquid sprayers (U.S. Pat. Nos. 3,451,252; 4,491,023; and 4,409,845), and a row planter calibration (U.S. Pat. No. 4,693,122). Griffith presents a review of the volumetric calibration of planting and agricultural equipment. In addition, a standard method of determining and reporting performance data using broadcast spreaders designed to apply granular materials on the soil is available (ASAE Standard 5341, "Procedure for Measuring Distribution Uniformity and Calibrating Granular Spreaders," 1989).
In the treatment of turgrass by homeowners and commercial personnel, the two most common types of granular applicators are (i) the gravity or drop-type spreaders; and (ii) the centrifugal or rotary spreaders. The centrifugal or rotary broadcast spreaders are particularly difficult to calibrate, especially for homeowners, when contrasted to the gravity or drop-type spreaders.
The methods for calibrating centrifugal or rotary broadcast spreaders are cumbersome and laborious. Two methods of calibration are most commonly employed. In one method, a known amount of material is put into the spreader and delivered to a known area. The material remaining in the spreader is weighed and the weight of the distributed material determined. The amount of material distributed per unit area is then determined. The procedure is repeated with varied spreader settings until the desired rate is obtained. Disadvantages of this method are that large amounts of material must be handled, material is wasted, the spreader must be inverted to empty the hopper with considerable difficulty, increased danger of exposure to material of the operator and to the environment, and the method is time consuming.
Another method for calibrating rotary broadcast spreaders involves spreading material over a known area of a smooth impervious surface. The spread material is then collected by sweeping and weighed. The application rate per unit area can then be calculated. This procedure is then repeated with changes in spreader setting until the desired rate is obtained. This method is limited by errors introduced by not collecting all dispensed material and/or collecting contaminants, by the danger of exposing the operator and the workplace to material, and by procedural time requirements.
The present invention overcomes the above-described disadvantages inherent with various apparatuses and methods of the prior art. The invention presents a calibrator apparatus for use with granular broadcast spreaders which permits rapid and accurate spreader calibration employing agricultural materials.